The present invention relates to a safety device, particularly for industrial machines, such as bending presses for cold working of metal plates.
Said bending presses are usually constituted by a supporting frame for a die, which is arranged approximately horizontally and is conveniently shaped; a tool, such as a blade or punch, is arranged above said die and is slidingly associated with said frame.
If a blank, such as a metal plate, a bent plate or a box-like component is positioned above the die, it is possible to actuate the descent of the tool so as to force a given deformation of said blank.
The blank can be subjected to a plurality of successive bending operations, one for each descent of the tool, even along axes that are not mutually perpendicular, until it assumes the intended shape.
In order to protect the safety of the operator assigned to positioning the blank on the die, safety devices are currently used which are based for example on the use of photocells.
In particular, it is known to arrange a pair of transducers, a transmitter and a receiver, along a line that crosses longitudinally the industrial machine at a height from the die that is slightly greater than the thickness of the metal plate and at a short distance from the region occupied by the blade or punch during descent.
The photocells are connected to a control center that is suitable to block the descent of the tool when the signal transmitted between said photocells is interrupted, accordingly indicating the presence of a foreign object proximate to said tool.
The main drawback of this conventional safety device is that said known type of photocell device in some circumstances halts the industrial machine even when the operator is completely safe.
In particular, one case that occurs frequently relates to the working of box-like components or in any case of blanks that have one or more bends for example at 90°.
In this circumstance, the portion of the blank that has already been worked protrudes above the flat portion to be worked, interposing between the two photocells and therefore causing an incorrect stop of production.
In such cases there is therefore the important drawback of having to deactivate said known type of protection device, performing the operation without any assurance for the safety of the operator.
This is a severe problem for protecting operator safety; said operators, in order to work certain parts, are forced to work for most of the time without any safety device.
This problem is worsened by the fact that after a few hours of work the attention of the operator necessarily decreases, entailing an increase in the already high danger level of the use of the machine.
In any case, the lack of safety regarding certain machining operations requires great attention in performing said operations and therefore a greater expenditure of resources and increased slowness with respect to an identical machining process performed in safe conditions.